1. Field of the Invention
The prevent invention relates to a method and apparatus for transporting vehicle bodies in a vehicle assembling line and further to a vehicle assembling system equipped with such transporting apparatus.
2. Description of the Prior Art
Vehicle assembling lines have been known, wherein many types of transporting means such as a floor type including a carriage and an overhead type including a hanger are arranged for every working section, so that various parts may be assembled to a body of a vehicle in these working sections while the body is transported and passed therethrough, for example, as disclosed in Japanese patent application Laid open No. 21871/86.
However, in carrying out the assembling in a certain Working section by use of an automatic machine such as a robot in such assembling lines, it is necessary to position the body transported by the transporting means relative to the automatic machine. For this reason, basic holes have been provided in the body, and positioning pins adapted to engage the basic holes have been mounted on the transporting means, so that the body could be positioned relative to the transporting means to provide a given positional relationship between the body and the automatic machine by stopping the transporting means in a predetermined position relative to the automatic machine.
In the above system, the following problem is encountered: the positioning pins of each of the transporting means must be inserted and withdrawn for each shifting of the body from one transporting means to another transporting means, and repetition of such insertion and withdrawing of the pins causes the basic holes to be deformed, resulting in reduced positioning accuracy, with a tendency for the body to be damaged.
Further, there is known transporting means which uses a self-travel carriage self travellable on a track laid on a Working floor (see Japanese patent application Laid-open No. 66833/82. Such arrangement is accompanied by the following problems:
(1) Attention must always be given that there is no obstacle on the track and in the vicinity thereof to permit the normally smooth travel of the self travel carriage, resulting in increased restrictions in providing a layout for an assembling line:
(2) The track occupies a wide space over the floor surface in a working site;
(3) Because the self travel carriage travels on the floor surface in the working site, an increased cost of equipment is required for extra safety for workers; and
(4) The track is a hindrance in carrying out working such as assembling of a body on the self-travel carriage from the below.
Furthermore, in coexistence with an automated assembling zone employing a number of automatic machines such as robots and a manually assembling zone in the above-described assembling line, an assembling system for use in such assembling line is known from Japanese patent application Laid-open No. 21869/86, wherein the assembling line is largely divided into three sections: a first half, a latter half and an end section, with a cart type conveyor being used in the first section to concentratively arrange automated asembling steps therein, a trolley type or power and free type conveyor being used in the second section to concentratively arrange manually assembling steps, and a tact carrying conveyor being used in the end section to arrange automated assembling steps following the manually assembling steps. However, such prior art assembling system is accompanied by the following problems:
(1) Three different types of body-transporting conveyors are required while the body is transported along the assembling line from its starting point to its terminal point, resulting in not only an increased cost of equipment but also reduced freedom in rearrangement of the assembling line;
(2) When a trouble is generated in the automatic machine such as robot problems in the automated assembling zone, it is impossible to deal with the trouble until the body has been passed through the automated asembling zone and hence, a preparative manually assembling zone must be specially provided therefor;
(3) The body is liable to be damaged, when it is transferred onto the different transporting means.